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Occasionally the longer axes of the
several ellipses extend in different directions, of which Acacia Farnesiana
offered a good instance. The following cases will give an idea of the rate
of movement: Oxalis acetosella completed two ellipses at the rate of 1 h.
25 m. for each; Marsilea quadrifoliata, at the rate of 2 h.; Trifolium
subterraneum, one in 3 h. 30 m.; and Arachis hypogaea, in 4 h. 50 m. But
the number of ellipses described within a given time depends largely on the
state of the plant and on the conditions to which it is exposed. It often
happens that a single ellipse may be described during one
[page 405]
day, and two on the next. Erythrina corallodendron made four ellipses on
the first day of observation and only a single one on the third, apparently
owing to having been kept not sufficiently illuminated and perhaps not warm
enough. But there seems likewise to be an innate tendency in different
species of the same genus to make a different number of ellipses in the
twenty-four hours: the leaflets of Trifolium repens made only one; those of
T.


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